1. Field of the Invention
The present invention relates to a refrigerant compressor used in a refrigeration cycle such as a refrigerator.
2. Description of the Related Art
As a refrigerant compressor used in a refrigeration cycle such as a refrigerator, there is a refrigerant compressor which includes a connecting rod attached with a crankpin and a piston pin at both ends thereof such that the crankpin and the piston pin are slidable, and converts an eccentric motion of the crankpin caused by a rotational motion of a crankshaft into a reciprocation motion of a piston, thereby obtaining a compression action. In the refrigerant compressor, the piston pin and a hole portion of the connecting rod are applied with a great surface pressure (load) during the compression action and thereby wear out.
As a solution to this, a sealed compressor is known, which includes an oil feed hole extending inside of a connecting rod, and an oil feed groove provided on a sliding surface of a piston pin which slides on a wall portion of a small end hole of the connecting rod so as to extend in a center axis direction of the piston pin, and positioned so as to communicate with the oil feed hole when the piston is moving from a top dead center to a bottom dead center (see, e.g., Japanese Patent No. 2783381).
FIG. 6 is a cross-sectional view of a piston device of the sealed compressor disclosed in Japanese Patent No. 2783381.
Referring to FIG. 6, the sealed compressor disclosed in Japanese Patent No. 2783381 includes a piston 2, a connecting rod 7 having a small end hole 8 at one end thereon and a large end hole 9 at the other end thereof, an oil feed hole 10 extending inside of the connecting rod 7 and providing communication between the small end hole 8 and the large end hole 9, a piston pin 22 slidably accommodated into the small end hole 8 and secured to the piston 2, and an oil feed groove 23 provided on a sliding surface of the piston pin 22 which slides of a wall portion of the small end hole 8 so as to extend in a center axis direction of the piston pin 22, and positioned so as to communicate with the oil feed hole 10 when the piston 2 is moving from a top dead center to a bottom dead center.
In this sealed compressor, during a compression stroke when a great load is applied to the sliding portion of the piston 22 and of the small end hole 8 of the connecting rod 7, the piston pin 22 contacts the small end hole 8 of the connecting rod 7 at a portion where the oil feed groove 23 is not provided, which makes it difficult for the sliding portion to wear out. During a suction stroke, the oil feed hole 10 of the connecting rod 7 and the oil feed groove 23 of the piston pin 22 conform to each other and are communicated with each other, thereby feeding an oil to the small end hole 8.
In the above stated sealed compressor, the oil feed hole 10 of the connecting rod 7 and the oil feed groove 23 of the piston pin 22 conform to each other and are communicated with each other, for a short time period. Therefore, there is a possibility that the oil is not fed to the small end hole 8 sufficiently. When the oil is not fed to the small end hole 8 sufficiently, a cooling effect provided by the oil is lessened, and insufficient lubrication due to the insufficient oil feeding and a temperature increase in the sliding portion may occur.